Diabetic nephropathy, the leading cause of renal failure in the United States, results from injury to the renal microvasculature. In this proposal, we use rodent models to investigate the protective role of ENTPD1 (also known as CD39) in renovascular disease, particularly diabetic nephropathy. ENTPD1 is a vascular ectonucleotidase that hydrolyzes ATP and ADP to AMP, thereby modulating extracellular nucleotide signaling via purinergic receptors. ENTPD1 is a protective factor in several models of acute and sub-acute vascular injury. We hypothesize that ENTPD1 is crucial in protecting the renal vasculature from chronic injury in diabetes. We also predict that the elusive mutant gene in a long-studied rat model of renal failure is ENTPD1. In Aim 1, we characterize the role of ENTPD1 in vascular protection in models of chronic vascular injury using mice null or transgenic for ENTPD1. By identifying the downstream pathways of injury driven by aberrant nucleotide signaling, we will begin to understand the mechanisms explaining ENTP1's protective effects against diabetic injury. In Aim 2, our goal is to show that reduced ENTPD1 enzymatic activity produces defects in autoregulation of renal blood flow in mouse models. Such defects are also associated with development of renal impairment in patients with diabetes. In Aim 3, we build evidence that a powerful Quantitative Trait Locus (QTL) for renal injury in rats is caused by a mutation in ENTPD1. We propose enzymatic activity assays, molecular genetics, and in vivo rescue experiments to prove this conjecture. This research will be performed predominantly at Beth Israel Deaconess Medical Center and Harvard Medical School in the lab of Simon Robson, M.D., Ph.D., a pioneer in the study of ectonucleotidases and purinergic signaling. Additional physiologic experiments will be performed by the applicant at the NIH in the laboratory of Jurgen Schnermann, M.D. The applicant's training and career development will be enhanced by coursework, conferences, seminar series, and other events in this stimulating academic environment. The applicant is a board-certified nephrologist with a passion for science and a firm commitment to translational research. This adventurous but focused research proposal and training plan will prepare the applicant for the transition to independence for a career in investigational medicine. The long-term scientific goal of this project is to understand how ENTPD1 might impact kidney disease in patients with diabetes. Our findings could eventually lead to early diagnosis and treatment of this devastating complication of diabetes.